Accuracy of a force sensitive digital tablet in determining the position of force application

In this paper, the accuracy in determining the position of force application with a novel force sensitive digital tablet is evaluated and improved. A loading system consisting of a strip-shaped board with a stylus and a plate with grid is used to apply a point load on the tablet. In static experiments, the stylus is placed on 49 equidistant locations respectively, and calibrated masses are used to exert vertical force from 0.25 N to 5 N. Dynamic experiments are also performed by means of drawing on the loading board. Experimental results show that the systematic error is nonlinearly dependent on the actual position of force application, and almost independent of the magnitude of exerted force vector. Dynamic experimental results also suggest that this tablet can determine the position as accurately in dynamic conditions as in static conditions. According to the observed error distribution, the measured positions are corrected using artificial neural network (ANN). The encouraging results of the correction indicate that the proposed correction procedure can provide significant improvement in the performance of the tablet in determining the position of force application.